This invention relates in general to driver circuits for electric actuators, such as rotary motors and linear actuators, and in particular to an improved structure for highly efficient, low cost driver circuit for such an electric actuator.
Electric actuators are well known devices which convert electrical energy to mechanical movement. To accomplish this, electric actuators establish and control electromagnetic fields so as to cause the desired mechanical motion. There are many different types of electric actuators, each utilizing different means for establishing and controlling these electromagnetic fields. One well known type of electric actuator is a rotary motor, in which the electrical energy is converted into rotational movement of a mechanical member. Another well known type of electric actuator is a linear actuator, in which the electrical energy is converted into linear movement of a mechanical member.
The two basic components of an electric rotary motor are (1) a stationary member, generally referred to as the stator, and (2) a rotatable member, generally referred to as the rotor. Typically, the rotor is supported for rotation within the stator. A plurality of radially inwardly extending poles are provided on the stator, while a plurality of radially outwardly extending poles are provided on the rotor. Depending upon the particular variety of electric motor, windings of an electrical conductor are provided on the poles of either the stator or the rotor, or on both. By generating pulses of electrical current through the windings in a proper manner, electromagnetic fields are created which interact with the stator and the rotor. These electromagnetic fields cause the rotor to rotate relative to the stator.
Similarly, the two basic components of an electric linear actuator are (1) a stationary member, generally embodied as an electromagnetic coil, and (2) a linearly movable member, generally referred to as the armature. Typically, the armature is supported for linear movement within the electromagnetic coil. By generating pulses of electrical current through the electromagnetic coil, electromagnetic fields are created which cause the armature to move linearly relative to the electromagnetic coil.
In both types of electric actuators, an external driver circuit is usually provided for generating the pulses of electrical current in a desired manner. Such driver circuits are typically connected between a source of electrical energy and the electric actuator. To generate a pulse of electric current, the driver circuit closes an electronic switch which allows electrical current to flow from the source of electrical energy to the electric actuator. The energy contained in this pulse of electrical current is converted into an electromagnetic field by the windings of the rotary motor or the coil of the linear actuator. A portion of that energy is then converted into mechanical energy so as to cause movement of the movable member of the electric actuator. When the electronic switch is subsequently opened, a portion of the energy contained in the winding or the coil remains stored therein as a continuing electromagnetic field.
Many different actuator driver circuits are known in the art. Some actuator driver circuits do not include any means for recovering the portion of the stored energy contained in the electromagnetic field when the electronic switch is opened. Consequently, actuator driver circuits of this type are inefficient. Other actuator driver circuits do include some means for recovering the portion of the stored energy contained in the electromagnetic field when the electronic switch is opened. However, it has been found that these types of actuator driver circuits are relatively complicated and expensive in construction. Also, it has been found that such actuator driver circuits are not readily adaptable for use with varying types of electric actuators. Accordingly, it would be desirable to provide an improved structure for an actuator driver circuit which is relatively high in efficiency, relatively low in cost, and readily adaptable for use with varying types of electric actuators.